Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – Having insulated gate
Reexamination Certificate
2001-08-13
2003-09-09
Dang, Phuc T. (Department: 2818)
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
Having insulated gate
C438S230000
Reexamination Certificate
active
06617204
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of forming a protective film to prevent a nitride read only memory cell charging, and more particularly, to a method of forming a nitride read only memory cell that the protective layers are formed in the inter-level dielectrics (ILD)/inter-metal dielectrics (IMD) layer.
BACKGROUND OF THE INVENTION
Referring to
FIG. 1
, it shows a cross-sectional view of the structure of the conventional nitride read only memory cell. The forming of the nitride read only memory cell, firstly the active area is defined on the substrate
100
by using photolithography and such methods as the wet etching. The phosphorous ions (P
−
) are doped into the substrate
100
by using the ion implantation to form the channel
124
. The first oxide layer
102
, the nitride layer
104
, and the second oxide layer
106
are deposited on the substrate
100
in turn, and the nitride layer
104
is located between the first oxide layer
102
and the second oxide layer
106
. The first oxide layer
102
, the nitride layer
104
, and the second oxide layer
106
are defined by using the photolithography and the etching process to form an oxide
itride/oxide (ONO) structure
108
and expose the substrate
100
.
The polysilicon layer
110
is deposited to cover the second oxide layer
106
, and the silicide layer
112
is deposited to cover the polysilicon layer
110
, then the polysilicon layer
110
and the silicide layer
112
are defined to expose the second oxide layer
106
by using photolithography and the etching process similarly, so that the gate
114
is formed. Next, a material layer, such as the tetra-ethyl-ortho-silicate (TEOS), the silicon dioxide (SiO
2
), or the silicon nitride (Si
3
N
4
) etc., is deposited, such as by the chemical vapor deposition (CVD) to cover the substrate
100
, the second oxide layer
106
, and the silicide layer
112
. The material layer is defined by using photolithography and the anisotropic etching process to form the spacer
116
.
Subsequently, the heavy highly concentrated doping and great depth is executed on the substrate
100
by using the structure consisted of the spacer
116
and the gate
114
as the mask, and the phosphorous (P) or the arsenic (As) that has greater solid solubility to the silicon (Si) as the ion source, so that the drain
122
and the source
126
are formed. An insulated layer
118
is deposited to cover the substrate
100
, the spacer
116
, and the silicide layer
112
, and the ILD/IMD layer
120
is deposited to cover the insulated layer
118
. Developed to this present, the nitride read only memory cell structure is completed.
For the following process, such as ultra-violet light or plasma usually penetrates through the nitride read only memory device to excite the atoms, so that the nitride read only memory device electrical instability results and damages the nitride read only memory device, or increases the ion mobility to cause the charge gain during the process, enhancing the threshold voltage, and affecting the stability of the device.
SUMMARY OF THE INVENTION
According to the conventional method of forming the nitride read only memory cell, there is no protective structure formed, so on the following process, the nitride read only memory cell may be penetrated through by the ultra-violet light or the plasma, and may increase the ion mobility to cause the charge gain, so that nitride read only memory cell damage will result and also result in the nitride read only memory cell electrical instability.
Accordingly, one aspect of the invention is to provide a method of forming the protective form to prevent a nitride read only memory cell charging. For nitride read only memory cell formation, the method of the present invention forms the protective layers to avoid the ultra-violet light and the plasma penetrating through the nitride read only memory device, to prevent the ion mobility increasing, and to keep the electricity's stability.
Another aspect of the invention is to provide a method of forming the protective film to prevent a nitride read only memory cell charging. For nitride read only memory cell formation, the method of the present invention forms one or a plurality of protective layers in the ILD/IMD layer to avoid the charge gain during the process, increasing the ion mobility, and the ultra-violet light or the plasma penetrating, so to enhance the electricity's stability of the device, decrease the nitride read only memory device's threshold voltage, and expand the threshold voltage range.
For at least the foregoing aspects discussed above, the present invention provides a method of forming the protective film to prevent a nitride read only memory cell charging. The present invention's method adds one or a plurality of protective layers, such as the silicon nitride (SiN
x
) layer or the silicon-oxy-nitride (SiON) layer, and the protective layers can resist the ultra-violet light illumination and the invading plasma, so that the nitride read only memory device cannot be excited to discharge in order to the ultra-violet light and the plasma, and decrease the device's threshold voltage, so the device's electricity can be controlled and kept constant.
REFERENCES:
patent: 5200354 (1993-04-01), Om et al.
patent: 5817557 (1998-10-01), Baldi
Chou Li-Yeh
Liu Chen-Chin
Sung Jiann-Long
Dang Phuc T.
Macronix International Co. Ltd.
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